The present invention relates to a semiconductor power device, more specifically, a an over-charge protection device.
In some applications for laser-diodes (e.g. welding) high laser power is necessary. This is achieved by electrically connecting many laser-diodes (e.g., 10 or more) in series, a solution that requires one power source or current source.
With series connection, one requires more acceptable, readily available voltage range for driving these laser diodes in series, 10 volts or more, rather than the low voltage, 1 volt to 3 volts that one such diode will need. The same argument holds for the series connection of light emitting diodes, (LED's), for lighting applications.
Another advantage of a series connection is higher power output compared to higher current in a parallel connection. For same power output in a parallel connection, the current is higher. For example, for 10 diodes in parallel, the current is 10 times higher than in a series connection, thus the conduction losses in the associated conductors are 100 times higher (power loss increases by the square law of current). A problem arises, however, when one of the laser-diodes, (or LED's) in a series-connection fails and is destroyed. This may make the entire device unusable although other nine diodes are in good operational condition.